A normal population has mean =μ7 and standard deviation =σ5. (a) What proportion of the population is less than 18?

P(x< 18) = 0.986

Step-by-step explanation:

Step 1: find the z-score using the formula, z = (x - µ)/σ

Where,

x = randomly chosen values = 18

µ = mean = 7

σ = standard deviation = 5

Proportion of the population that is less than 18 = P(x < 18)

Plug in the values into z = (x - µ)/σ, to get z-score.

z = (18 - 7)/5

z = 11/5 = 2.2

Step 2: Find P(x< 18) = P (z<2.2) using z-table.

The probability that corresponds with z-score calculated is 0.986.

Therefore,

P(x< 18) = 0.986